The Jaguars’ new defense doesn’t have a name yet and still had the look of an experiment during training camp.

But if the defense during a 12-9 loss to the Miami Dolphins in their preseason opener Monday night was any indication, the Jaguars are serious about using something of a hybrid this year that’s a mixture of the 4-3 and the 3-4.

Still, it no longer appears to be an experiment. It appears to be the defense the Jaguars are going to use this year.

The Jaguars don’t have the big tackles inside to play the classic 4-3 defense the way they did when Marcus Stroud and John Henderson were leading the line.

On the other hand, they don’t have the personnel to play the 3-4 exclusively, either, so they’re apparently going to try to keep teams off balance by mixing and matching.

“We understand we have some guys that are better suited for that [3-4], and there are other guys that are better suited for a 4-3. So, we’ll pick our spots,” Del Rio said.

Sometimes, the defense will line up with four linemen with their hands on the ground in the traditional 4-3. Sometimes there are three linemen with their hands on the ground with two potential rushers lined up next to them. But sometimes, one of them will drop back into coverage.

Del Rio didn’t want to go into specifics.

“I’m not going to sit up here and describe our defense in detail for our opponents. But we’re going to utilize our guys and put them in position to make plays,” he said.

The defense received mixed reviews in the first game. The Jaguars held the Dolphins to two field goals in the first half, but Miami controlled the ball for 17 minutes, 21 seconds.

The Jaguars didn’t register a sack, but they stopped the running game in the first half, holding Ricky Williams to 31 yards in 10 carries and Ronnie Brown to 10 yards in four carries.

Fourteen of Miami’s 50 first-half rushing yards came on an end around by wide receiver Ted Ginn Jr.

“I thought that [run defense] was solid from some of the things that we’ve worked on in camp in terms of being physical in the trenches,” Del Rio said.

The defense might have been more impressive if Brian Williams hadn’t drawn a 34-yard pass-interference penalty when the Jaguars had the Dolphins pinned back on their 1 in the first quarter.

“He got out of whack there a little bit,” Del Rio said. “The play coming off the goal line, just use your veteran savvy, and you’re in position, knock the ball down. And then [they] followed it up with a reverse where he was in position and kind of lost his footing. … We’re in preseason, you don’t want to get too carried away, but, yeah, there were a couple of things that we certainly need to see him get better.”

Williams is in a duel with rookie Derek Cox for the starting cornerback job. Cox was held out of the game with a groin pull, even though he made the trip.

The Jaguars’ original thought was to play Cox, but then they decided to give him more time to heal.

The play of Williams, who also had a face-mask penalty, wasn’t related to the changing alignments.

It was interesting that Del Rio used the new defense in the first preseason game because opposing teams can have a look at it. Del Rio is more interested in getting his players used to it than in hiding it.

“We’re just going to work on our defense,” Del Rio said. “We’re just going to play some defense and work on it and not really worry about how it’s discussed. … We do feel like there are some fronts that can help us generate pressure on the quarterback, and I think in order to be able to do that, you’re going to be able to stop the run.”

Defensive end Reggie Hayward said the 3-4 has become trendy around the league, but the Jaguars couldn’t just switch exclusively to that.

“You’ve got to introduce it,” Hayward said. “It can’t be just a complete changing of the guard. A lot of us are unfamiliar with the 3-4 style. It’s a slow progression. You try to introduce it to the players and see where it goes.”

It still appears to be uncertain how many of these alignments the Jaguars will use in the regular season.

“It’s just too early to start putting labels on what you’re going to be and stuff like that,” Hayward said. “We have a long way to go.’

The Jaguars return to work today and will conduct their final two two-a-day practices today and Thursday.